Authorities arrested two teenage boys after they were accused of plotting a Columbine-style school mass killing, WINK-TV reports.

What are the details?

Police arrested 13-year-old Connor Pruett and 14-year-old Phillip Byrd after investigators discovered that the two were plotting to execute a mass killing at Harns Marsh Middle School in Lehigh Acres, Florida.

Authorities detained the two on Thursday after a school resource officer at the school was notified that one of the students had a gun in his backpack. While authorities did not find any weapons on either suspect, investigators said they did determine that the two extensively planned an attack to take place at the school. An investigation found that the two students amassed guns, ammunition, knives, and a detailed map of the school’s interior and its surveillance cameras.

Connor and Phillip both appeared in front of a Lee County judge on Sunday after being taken into custody on Saturday.

Both teen suspects will be held for at least 21 days in secure juvenile detention, where they will undergo an extensive mental health evaluation.

Phillip’s mother, Carrie Tuller, appeared in court on Sunday, where she defended her son.

“He’s just a little boy,” she said. “He didn’t think this was really serious. He didn’t think they were serious.”

The two teens are due in court on Sept. 27.

‘This could have turned disastrous’

According to WTVD-TV, Lee County Sheriff Carmine Marceno said that the two were “extensively studying” the 1999 mass killing that took the lives of at least 13 people and were also studying how to construct pipe bombs.

“This could have turned disastrous,” Marceno said during a Thursday press conference. “We were one second away from a Columbine here. … We stopped them in the planning stages.”

Both teens were well known to authorities, and deputies previously visited their homes a combined total of nearly 80 times.

They will face charges of conspiracy to commit a mass shooting, Marceno added.

Lee County Superintendent Ken Savage said that the students who came forward with the information along with the fast-acting teachers may have saved lives.

“Students were safe at all times,” Savage said. “All the threat assessment and emergency response training made a difference in the outcome of this incident.”

Principal Alex Dworzanski told WBBH-TV that the school has been deemed safe for students to return to classes.

“I commend the students who came forward to report the threat and the quick action of the staff,” Dworzanski said. “The safety of our students and staff is at the core of what we do.”